The invention relates to coolant pumps in a cooling circuit of an internal combustion engine including a first coolant pump driven by the internal combustion engine and a second coolant pump which can be coupled to the first coolant pump by a clutch.
DOS 1 476 365 discloses a coolant pump with two co-axial impeller wheels. The first impeller wheel is firmly mounted onto a drive shaft whereas the second impeller wheel can be connected to first impeller wheel by a pressure-controlled clutch wherein the control pressure for the clutch depends on the temperature of the liquid being pumped.
It is the object of the present invention to provide a coolant pump arrangement by which optimal cooling of the engine and small power consumption is ensured.